PATIENT CHARACTERISTICS: Age: 18 and over Performance status: WHO 0-1 Life expectancy: More than 12 weeks Hematopoietic: Neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: No unstable or uncompensated hepatic disease Bilirubin less than 1.25 times upper limit of normal (ULN) Albumin at least lower limit of normal ALT or AST no greater than 2.5 times ULN (5 times ULN if liver metastases present) Renal: No unstable or uncompensated renal disease Creatinine clearance at least 60 mL/min Cardiovascular: No unstable or uncompensated cardiac disease Pulmonary: No unstable or uncompensated respiratory disease Other: No concurrent intestinal obstruction No evidence of severe or uncontrolled systemic disease No other active malignancy within the past 5 years except squamous cell or basal cell skin cancer or carcinoma in situ of the cervix No severe concurrent condition that would preclude study compliance No risk of transmitting HIV or hepatitis B or C Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception